Hello,at first your client must load instance of Order by your findByKey() method. Now you have detached Order instance with collection of LineItems (assume Eager loading). Now you change something in LineItems collection, for example product name. Next call update() method of your session bean but with your detached local client Order as parameter.

This is very inefficient way of managing your entities with relations as introduces extra layer of complexity in the code. Anyways, the persistence specification section 2.1.7 says following:

"The container handles the object-relational mapping of the relationships, including their loading and storing to the database as specified in the metadata of the bean class, and the referential integrity of the relationships as specified in the database (e.g., by foreign key constraints)."

With this i suppose the current limitation is only temporary untill someone fixes it.